Multi-Coil Field Generation In An Electronic Contact Lens System

ABSTRACT

An augmented reality system includes an electronic contact lens and a plurality of conductive coils to be worn, for instance, around a neck, around an arm, or on a chest of a user. The conductive coils can inductively couple to the electronic contact lens by producing magnetic fields that the electronic contact lens can convert into power. A direction of the resulting magnetic at the electronic contact lens can rotate over time, enabling the electronic contact lens to periodically form a strong inductive coupling with the plurality of conductive coils despite the orientation of the electronic contact lens. The electronic contact lens can also output a feedback signal representative of the power produced at the electronic contact lens or an orientation signal representative of the orientation of the eye, and the magnetic fields produced by the conductive coils can be altered based on the feedback signal or orientation signal.

BACKGROUND 1. Technical Field

One or more embodiments of this disclosure relate to the wirelesstransmission of power to an electronic contact lens.

2. Description of Related Art

Augmented reality (AR) adds computer-generated information to a person'sview of the world around them. One type of AR system includes anelectronic contact lens, for instance using tiny video projectors (or“femtoprojectors”) as described in Deering (U.S. Pat. No. 8,786,675).Generally, electronic contact lenses can't accommodate batteries ofsufficient capacity to power the electronic contact lenses for verylong. Accordingly, providing power to the electronic contact lenseswirelessly is an attractive alternative, and represents an active areaof research and development.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the disclosure have other advantages and features whichwill be more readily apparent from the following detailed descriptionand the appended claims, when taken in conjunction with the accompanyingdrawings, in which:

FIG. 1 shows a person wearing an augmented reality system including anecklace.

FIG. 2A shows a necklace of an augmented reality system.

FIG. 2B shows a representation of the control electronics containedwithin the necklace of an augmented reality system.

FIG. 3A shows a plan view of a contact lens display mounted on aperson's eye.

FIG. 3B shows a cross-sectional view of a contact lens display mountedon a person's eye.

FIG. 3C shows a plan view of the contact lens display of FIG. 3A in moredetail.

FIG. 4 is a diagram illustrating a strong inductive coupling and a weakinductive coupling between conductive coil pairs.

FIGS. 5A-5C show various orientations of an eye wearing an electroniccontact lens in the presence of a magnetic field as the eye moves withinthe eye socket.

FIGS. 6A-6C show the relative coupling strength between an electroniccontact lens and a necklace producing a magnetic field for the relativeeye orientations of FIGS. 5A-5C, respectively, as a user's head tiltsupwards and downwards.

FIG. 7 shows a cross-section view of system with two conductive coilsfor providing power to an electronic contact lens.

FIG. 8 shows a rotating magnetic field produced by the system of FIG. 7.

FIG. 9A shows a side view of a system with three conductive coils forproviding power to an electronic contact lens.

FIG. 9B shows a front view of a system with three conductive coils forproviding power to an electronic contact lens.

FIGS. 10A and 10B show rooms with multiple conductive coils forproviding power to an electronic contact lens.

FIG. 10C shows an interior of a car with multiple conductive coils forproviding power to an electronic contact lens.

FIG. 11 shows a measured voltage provided to a simulated electroniccontact lens at various contact lens orientations in the presence ofboth a stationary magnetic field and a rotating magnetic field.

The figures depict various embodiments for purposes of illustrationonly. One skilled in the art will readily recognize from the followingdiscussion that alternative embodiments of the structures and methodsillustrated herein may be employed without departing from the principlesdescribed herein.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Electronic contact lenses can include devices or components that requirea power source to operate. For example, an electronic contact lens caninclude tiny projectors, such as femtoprojectors, to project images ontothe user's retina. If the contact lens display is partially transparent,then the image from the femtoprojector is combined with the externalscene viewed by the user though the contact lens, thus creating anaugmented reality.

One way that power can be supplied to an electronic contact lens isthrough magnetic induction. An energy source, for instance a source coilworn as a necklace, can produce a time-varying magnetic field (“TVMF”).An electronic contact lens including a reciprocal coil can inductivelycouple to the energy source by converting current in the reciprocal coilcaused by the TVMF into power. However, the amount of power produced bythe contact lens depends on the angle between the contact lens and thedirection of the magnetic field. In other words, the coupling betweenthe contact lens and the energy source is strongest when the directionof the TVMF is orthogonal to plane of the contact lens coil, and isincreasingly weaker as this angle decreases.

In practice, the orientation of an electronic contact lens willfrequently change as the eye wearing the lens moves relative to thepower source. Accordingly, when the TVMF produced by the power source isrelatively stable, the orientation of the contact lens relative to thedirection of the TVMF will change over time, thereby changing thestrength of coupling between the contact lens and the power source overtime. Unfortunately, during periods of time when the strength ofcoupling between the contact lens and the power source is relativelyweak, the amount of power available to the contact lens may be reduced.

To address such instances, the power source can include multipleconductive coils, each configured to produce a TVMF in a differentdirection. The direction of the resulting TVMF at the contact lens canrotate, for instance if the conductive coils are driven with currents atthe same frequency but with a phase difference. The conductive coils canbe driven autonomously to produce a rotating magnetic field, forinstance without feedback from the contact lens. As discussed below, arotating magnetic field can increase an amount of power produced by thecontact lens relative to a stationary magnetic field.

A sensor (for instance, embedded within the contact lens or external tothe contact lens) can provide feedback to the power source. Based onthis feedback, the magnetic fields produced by the conductive coils ofthe power source can be adjusted so that the resulting magnetic field atthe contact lens is pointed in a different direction. For instance, apower sensor can provide an indication of an amount of power produced bythe contact lens to the power source, which in turn can adjust themagnitude of current provided to one or more of the conductive coils ofthe power source. Another type of feedback identifies an orientation ofthe contact lens, and the power source can vary the magnetic fieldsproduced by the conductive coils based on this orientation.

The figures and the following description relate to preferredembodiments by way of illustration only. It should be noted that fromthe following discussion, alternative embodiments of the structures andmethods disclosed herein will be readily recognized as viablealternatives that may be employed without departing from the principlesof what is claimed.

FIG. 1 shows a person wearing an augmented reality system 100 includinga visible necklace 110. Even though the necklace 110 is in plain sight,it may be designed to look like ordinary jewelry and therefore attractsno special notice. In some configurations, the necklace can be hiddenunderneath the wearer's clothes. Whatever the design of the necklace110, it does not alter one's impression of the person wearing it. Theirappearance other than the addition of the necklace 110 is not affectedby the AR system.

Furthermore, the AR system of FIG. 1 does not disturb the wearer. Thecontact lens displays 120 may also function as regular contact lensesproviding refractive eyesight correction if required. The necklace 110is lightweight and may not need to be held in one's hand like a cellphone or tablet. When the contact lens displays 120 are not showingimages, the wearer is hardly conscious of the AR system 100. When the ARsystem 100 is displaying images, reacting to speech or receivingmessages, it provides functions like that of a smartphone but in a morenatural way.

In the illustrated necklace 110 of FIG. 1, the necklace 110 includeshardware elements 140 distributed about a band of the necklace 110 whichallows for a broader range of necklace designs suitable to a variety ofaesthetic tastes. Generally, the band includes a surface configured tobe placed against the wearer of the necklace 110 when the necklace 110is worn about the neck. In other configurations, the necklace includeshardware elements localized to a pendant of the necklace (as in FIG.2A). Generally, the pendant may be an ornamental object hanging from thenecklace 110 that is configured to enclose and conceal the hardwareelements 140 of the AR system 100.

While the AR system 100 is illustrated with a necklace 110, in otherembodiments the functions of the necklace 110 described herein can beintegrated into another type of wearable device. As an example, thefunctionality of the necklace 110 can be embedded in a necktie, a scarf,a belt, the brim of a hat, the collar of a shirt, the hood of a jacket,the sleeve of a sweater, the front of a t-shirt, etc. Alternatively, thenecklace 110 can be coupled to an external electronic device (notpictured) such as a smart phone and the coupled electronic device mayfacilitate functionality of the AR system 100.

FIG. 2A shows a necklace 110 of an unobtrusive augmented reality system100. In the illustrated embodiment, the necklace 110 includes a coil 210of conductive material such as an insulated wire and an electronicmodule 220 (“conductive coil” hereinafter). Module 220 contains thehardware elements 130 for controlling the augmented reality system 100.In some configurations, the module 220 is a pendant of the necklace. Inother configurations, the necklace 110 does not include a module 220 andthe hardware elements 140 are distributed about the circumference 230 ofthe necklace (i.e., as in FIG. 1). While not illustrated, the conductivecoil 210 and module 220 can be incorporated into the band of thenecklace. In some cases, the circumference 230 of the necklace is theinner diameter of the necklace band.

Additionally, the number of conductive loops in necklace coil 210 ischosen considering factors such as power requirements of contact lensdisplays 120, operating frequency, etc. The number of loops in necklacecoil 210 can be, for example, between 1 and 20 loops, which each loopincluding as many as 2500 or more insulated strands connected inparallel. In some configurations, an unlicensed frequency band can beused to couple the necklace 110 to the contact lens display 120, but anyother frequency can be used. In one example, the system can use anindustrial, scientific, and medical radio band (ISM).

Furthermore, conductors in the coil 210 may extend around thecircumference 230 of the necklace 110 for one, two, three, or moreloops. These loops may be connected or disconnected with a plug 240 andsocket 250 when putting the necklace 110 on or taking it off. Connectingthe plug 240 to the socket 250 allows data and power to be transmittedbetween the necklace 110 and contact lens display 120, and disconnectingthe plug 240 from the socket 250 prevents data and power from beingtransmitted between the necklace 110 and contact lens display 120.Generally, the coil 210 is configured to be worn around a user's neck asa necklace 110 when the plug 240 and socket 250 are connected. In someconfigurations, the necklace 110 does not include a plug 240 and socket250 but still allows for data and power to be transmitted between thenecklace 110 and contact lens display 120. In these configurations, anyother means of controlling data and power transfer can be included(e.g., a switch, a button, etc.).

In various embodiments, as a wearer of necklace 110 operates the ARsystem 100 and moves through the environment, the orientation ofnecklace 110 may vary with that movement (i.e., the shape of the band ofnecklace may change, relative orientations of the hardware elements 140in necklace 110 change, etc.).

FIG. 2B shows a necklace 110 of the augmented reality system 100. In theillustrated embodiment, the necklace 110 includes a module 220 that mayhave an exterior appearance of jewelry or a fashion accessory. However,the module 220 may contain additional hardware elements 140 such as: apower source such as a battery; a modulator to drive a radio-frequencycurrent in the necklace coil; a data modem to encode data on theradio-frequency signal; sensors such as microphones, cameras, inertialsensors, GPS receivers, barometric pressure sensors, etc.; a cellularradio; a Wi-Fi radio; a Bluetooth radio; a graphics processing unit;and/or, a microprocessor and memory. In other configurations, thehardware elements 140 included in module 220 may be distributed aboutthe necklace band.

When the hardware elements 140 produce a radio-frequency current (or anyother alternating current) in the necklace coil 210, power may beinductively coupled into a lens coil embedded in a contact lens display120. Data may also be transmitted to the contact lens display 120 bymodulating the radio-frequency current in the necklace coil 210.Amplitude, frequency, and phase modulation are examples of modulationschemes that may be employed. For example in frequency shift keying, apair of discrete frequencies are used to indicate logical “0” andlogical “1”.

The hardware elements 140 may include a microphone (or multiplemicrophones) to sense voices and other sounds. The wearer of anaugmented reality system 100 may control the system by speaking to it,for example. The system 100 may also include hardware elements 140 suchas a speaker and/or wireless connection to earphones. The system 100 maybe controlled via a touch sensor in the necklace or via gesturesdetected by hardware elements 140 including radar (e.g. 60 GHz radar),ultrasonic and/or thermal sensors.

Additional hardware elements such as inertial (acceleration and rotationrate) sensors, coupled with a barometric pressure sensor and a GPSreceiver may provide position and velocity data to the AR system 100.Further, cellular radio and/or Wi-Fi radio hardware elements can provideconnections to voice and/or data networks. Finally, a processor,graphics processing unit and memory can run applications and store data.Broadly, the hardware elements 140 are configured to transmit data andimages for projection by a contact lens display 120 onto a wearer'sretina.

When the AR system 100 is connected to an external electronic device,any of the sensors, processors and other components mentioned above maybe located in the electronic device. Alternatively, the hardwareelements 140 of the necklace 110 may connect to an electronic devicewirelessly or it may connect physically via a plug-and-socket connectoror another type of connector.

FIG. 3A shows a contact lens display 120 mounted on a person's eye. Thecontact lens display 120 includes a femtoprojector 310 mounted in acontact lens 320, and a conductive coil (or “lens coil”) 330 near theedge of the contact lens 320 for receiving power and data wirelesslyfrom the necklace 110 as in FIGS. 2A-2B. The femtoprojector 310 mayinclude electronics for harvesting power from the lens coil 330 in thecontact lens 320, processing data transmitted to the contact lens 320,and driving a light emitter inside the femtoprojector 310. Thefemtoprojector 310 projects images on a wearer's retina.

FIG. 3B shows a cross-sectional view of a contact lens display 120containing a femtoprojector 310 in a contact lens 320. FIG. 3B shows anembodiment using a scleral contact lens but the contact lens does nothave to be scleral (i.e., it could be a soft contact lens). The contactlens 320 is separated from the cornea of the user's eye 340 by a tearlayer 342. The contact lens display 120 has an outer surface facing awayfrom the eye 340 and an inner surface contacting the tear layer 342.Generally, the femtoprojector 310 is positioned between the frontsurface and the back surface of the contact lens 320. The contact lens320 preferably has a thickness that is less than 2 mm, and thefemtoprojector 310 preferably fits in a 2 mm by 2 mm by 2 mm volume. Thecontact lens 320 is comfortable to wear and maintains eye health bypermitting oxygen to reach the user's eye 340.

FIG. 3C shows the contact lens display 120 of FIGS. 3A-3B in moredetail. FIG. 3C shows a frontal view of a contact lens display 120 withmultiple femtoprojectors 310A-310C in a contact lens 320. The conductivecoil 330 in the contact lens 320 may have between about 1 and about 200loops arranged in a spiral and which extend along a peripheral region ofthe contact lens display 120. In other configurations, the conductivecoil 330 can be arranged in a cylindrical coil or any other loopedshape. The conductive coil 330 is connected to the femtoprojectors 310and other electronics via embedded connectors 332. The femtoprojectors310 are located in a central region of the contact lens display 120which is surrounded by the conductive coil 330. The femtoprojector 310,conductive coil 330, and electronics are enclosed in lens material suchthat the lens feels to a wearer like a conventional contact lens. Thecontact lens 320 is between about 6 mm and about 25 mm in diameter andpreferably between about 8 mm and about 16 mm in diameter.

The ratio of the contact lens 320 diameter to femtoprojector 310 lateralsize can be roughly 25:1 for the largest femtoprojector. This ratio isnormally between about 15:1 and 30:1, but may be as small as 5:1 or aslarge as 50:1. FIG. 3C shows three femtoprojectors 310A-C in the contactlens 320, but many femtoprojectors, or only one, may be mounted in sucha contact lens 320. Eye-mounted displays with as many as 49femtoprojectors in a contact lens 320 have been proposed. If there isonly one femtoprojector 310 in a contact lens 320, it need not be in thecenter of the lens.

The femtoprojectors 310 in FIG. 3C are also shown as different sizes.The entire display, made up of all the femtoprojectors 310, may be avariable resolution display that generates the resolution that eachregion of the eye can actually see, vastly reducing the total number ofindividual “display pixels” required compared to displays of equalresolution and field of view that are not eye-mounted. For example, a400,000 pixel eye-mounted display using variable resolution can providethe same visual experience as a fixed external display containing tensof millions of discrete pixels.

In FIG. 3C, the contact lens 320 is roughly divided by the dashed circleinto an optical zone 322 and a non-optical zone 324. Components in theoptical zone 322 may be in the optical path of the eye 340, depending onhow far open the iris is. Components in the non-optical zone 324 falloutside the aperture of the eye 340. Accordingly, active opticalelements are generally positioned in the optical zone 322 and non-activeoptical elements are positioned in the non-optical zone 324. Forexample, femtoprojectors 310 are within the optical zone 322 while theconductive coil 330 is in the non-optical zone 324. Additionally, thecontact lens 320 may also contain other components positioned in thenon-optical zone 322 for data processing, data transmission, and powerrecovery and/or positioning. As an example, an integrated circuit (IC)312 is positioned in the non-optical zone 324 and is connected to thefemtoprojectors 310.

The contact lens display 120 can also include other components such asantennae or optical/infrared photodetectors, data storage and buffering,controls, and possibly also on-lens processing components. The contactlens display can include positioning components such as accelerometersand fiducial or other structures used for eye tracking and headtracking. The contact lens display 120 can also include data processingcomponents, and can include a microprocessor or other data processingelements.

There are many ways in which the functions of receiving power and dataand projecting the data onto the retina of a wearer can be configuredwith an eye-mounted display(s) to create embodiments of eye-mounteddisplay systems. Portions of these subsystems may be external to theuser, while other portions may be worn by the user in the form of aheadpiece or glasses. Components may also be worn on a belt, armband,wrist piece, necklace or other types of packs. Some components may beincluded in external devices such as a watch, a cell-phone, a laptop,etc.

FIG. 4 is a diagram illustrating a strong inductive coupling and a weakinductive coupling between conductive coil pairs. The strong inductivecoupling is between a first source conductive coil 400A and a firstreciprocal conductive coil 402A. The first source conductive coil 400Agenerates a TVMF in a direction indicated by the vector {right arrowover (H)}_(A). The vector {right arrow over (H)}_(A) is orthogonal tothe plane defined by the first reciprocal conductive coil 402A. Stateddifferently, the unit vector {circumflex over (n)}_(A) that isorthogonal to the plane defined by the first reciprocal conductive coil402A is parallel to the vector {right arrow over (H)}_(A). As a result,the inductive coupling between the first source conductive coil 400A andthe first reciprocal conductive coil 402A, represented by the dotproduct Ĥ_(A)·{circumflex over (n)}_(A)˜1, is a strong coupling, whereĤ_(A) is the unit vector in the direction of {right arrow over (H)}_(A).

The weak inductive coupling illustrated by FIG. 4 is between a secondsource conductive coil 400B and a second reciprocal conductive coil402B. The second source conductive coil 400B generates a TVMF in adirection indicated by the vector {right arrow over (H)}_(B). The vector{right arrow over (H)}_(B) is parallel to the plane defined by thesecond reciprocal conductive coil 402B. Stated differently, the unitvector {circumflex over (n)}_(B) that is orthogonal to the plane definedby the second reciprocal conductive coil 402B is orthogonal to thevector {right arrow over (H)}_(B). As a result, the inductive couplingbetween the second source conductive coil 400B and the second reciprocalconductive coil 402B, represented by the dot product Ĥ_(B)·{circumflexover (n)}_(B)˜0, is a weak coupling.

A strong inductive coupling is a coupling between conductive coils inwhich the angle e between the direction of the TVMF produced by a firstconductive coil and a vector orthogonal to a second conductive coil iszero or close to zero (e.g., 20 degrees or less, 10 degrees or less, andthe like), and results in an increased amount of wireless power transferrelative to a weak inductive coupling. Likewise, a weak inductivecoupling is a coupling between conductive coils in which the angle ebetween the direction of the TVMF produced by a first conductive coiland a vector orthogonal to a second conductive coil is 90 degrees orclose to 90 degrees (e.g., 70 degrees or more, 80 degrees or more, andthe like). As noted above, the strength of an inductive coupling betweenconductive coils is proportional to the cosine of the angle e betweenthe direction of the TVMF produced by a first conductive coil and avector orthogonal to a second conductive coil.

Referring back to FIG. 1, the necklace 110 (a source conductive coil)can generate a TVMF, and can transmit power and/or data to the contactlens display 120 (a reciprocal conductive coil) via inductive coupling.Generally, the necklace 110 is worn around a user's neck duringoperation of the AR system 100. As a result, the direction of the TVMFproduced by the necklace 110 is generally consistent, and the strengthof coupling between a contact lens worn by a wearer of the necklace andthe necklace itself varies as the orientation of the contact lensrelative to the necklace varies.

FIGS. 5A-5C show various orientations of an eye wearing an electroniccontact lens in the presence of a magnetic field as the eye moves withinthe eye socket. In the example of FIG. 5A, an eye is looking upwards,and the angle between the direction of the TVMF {right arrow over(H)}_(A) produced by a necklace 110 and the vector {circumflex over(n)}_(A) orthogonal to the plane defined by a reciprocal coil of acontact lens is θ_(A). In the example of FIG. 5B, an eye is lookingforwards, and the angle between the direction of the TVMF {right arrowover (H)}_(B) produced by a necklace 110 and the vector {circumflex over(n)}_(B) orthogonal to the plane defined by a reciprocal coil of acontact lens is θ_(B). Finally, in the example of FIG. 5C, an eye islooking forwards, and the angle between the direction of the TVMF {rightarrow over (H)}_(C) produced by a necklace 110 and the vector{circumflex over (n)}_(C) orthogonal to the plane defined by areciprocal coil of a contact lens is θ_(C). In the examples of FIGS.5A-5C, the angle θ_(A) is smaller than the angle θ_(B), which in turn issmaller than the angle θ_(C); as a result, the coupling illustrated inFIG. 5A is stronger than the coupling illustrated in FIG. 5B, which inturn is stronger than the coupling illustrated in FIG. 5C.

FIGS. 6A-6C show the relative coupling strength between an electroniccontact lens and a necklace producing a magnetic field for relative eyeorientations of FIGS. 5A-5C, respectively, as a user's head tiltsupwards and downwards (and with a fixed eye orientation relative to theuser's head). It should be noted that the change in relative orientationillustrated in FIGS. 5A-5C may be due to the movement of the eye withinthe socket and the change in orientation illustrated in FIGS. 6A-6C maybe due to the movement of head, movement of the eyes relative to thehead, or a combination of the two. The orientations of the eye relativeto the power source shown in FIGS. 5A-5C are approximately equal to theorientations of the eye shown in FIGS. 6A-6C. In the example of FIG. 6A,which illustrates the eye orientation of FIG. 5A, the strength of theinductive coupling between the necklace and contact lens is representedby the dot product Ĥ_(A)·{circumflex over (n)}_(A). In the example ofFIG. 6B, which illustrates the eye orientation of FIG. 5B, the strengthof the inductive coupling between the necklace and the contact lens isrepresented by the dot product Ĥ_(B)·{circumflex over (n)}_(B), which isless strong than the inductive coupling illustrated in FIG. 6A.Likewise, in the example of FIG. 6C, which illustrates the eyeorientation of FIG. 5C, the strength of the inductive coupling betweenthe necklace and the contact lens is represented by the dot productĤ_(C)·{circumflex over (n)}_(C), which is less strong than the inductivecoupling illustrated in FIG. 6B.

In order to compensate for the varying eye orientations of a userwearing an electronic contact lens (and the resulting changes instrength of inductive coupling between the contact lens and thenecklace), a user can wear a power source that includes two conductivecoils arranged a different orientations. FIG. 7 shows a cross-sectionview of a system with two conductive coils for providing power to anelectronic contact lens 120. The system of FIG. 7 includes a firstsource conductive coil 702 worn around a neck of a user and a secondsource conductive coil 704 worn on a chest of the user. Each sourceconductive coil 702 and 704 produce a corresponding TVMF, and as thesource conductive coils 702, 704 are worn in different orientations, thedirections of each corresponding TVMF produced by the source conductivecoils 702, 702 are different.

The embodiment of FIG. 7 further includes a controller 700 configured todrive current through the source conductive coils 702 and 704. Thecontroller 700 is illustrated as a single controller, but it should benoted that in practice, the controller can include two or morecontrollers, for instance one for each source conductive coil to drivecurrent independently in each coil. The controller 700 is also shown asexternal to, but coupled to, each source conductive coil, but inpractice, a controller can be implemented within the same necklace as asource conductive coil. Although not illustrated in the embodiment ofFIG. 7, the controller 700 can include components such as a power source(such as a battery) from which the controller can draw power to drivesource conductive coils, a transceiver enabling the controller to sendand receive signals to and from the contact lens 120 or any otherentity, or any other components necessary to enable the controller toperform the functions described herein.

In the embodiment of FIG. 7, the controller 700 drives the sourceconductive coils 702 and 704, for instance with alternating currentsthat cause each source conductive coil to produce a TVMF. Each sourceconductive coil, in response to an alternating current with a positivemagnitude being driven through the source conductive coil, produces amagnetic field in a first direction orthogonal to the plane defined bythe source conductive coil. Likewise, each source conductive coil, inresponse to an alternating current with a negative magnitude beingdriven through the source conductive coil, produces a magnetic field ina second direction opposite the first direction. As the magnitude of thealternating current being driven through a source conductive coilincreases and decreases, for instance sinusoidally, the resultingmagnitude of the magnetic field produced by the source conductive coilsinusoidally increases and decreases, alternating between a firstmaximum magnitude in the first direction and a second maximum magnitudein the second direction opposite the first direction.

In some embodiments, the controller 700 can drive alternating currentsthrough the source conductive coils 702 and 704 such that the directionof the magnetic field at the contact lens 120 resulting from the TVMFsproduced by the source conductive coils 702 and 704 (the “resultingmagnetic field” hereinafter) rotates over time. For instance, thecontroller 700 can drive a first alternating current through the sourceconductive coil 702 at a particular frequency, and can drive a secondalternating current through the source conductive coil 704 at the samefrequency, but with a phase difference between the first alternatingcurrent and the second alternating current. The end result is that thedirection of the net magnetic field resulting from the collective effectof the TVMFs produced by the source coils 702 and 704 rotates at thesame frequency as the alternative current with which the sourceconductive coils are driven as a result of the phase difference betweenthe alternating currents.

FIG. 8 shows a rotating magnetic field {right arrow over (H)} producedby the system of FIG. 7. In the embodiment of FIG. 8, the resultingmagnetic field {right arrow over (H)} produced by the source conductivecoils 702 and 704 of FIG. 7 is illustrated at five distinct times: t₁,t₂, t₃, t₄, and t₅. At time t₁, the direction of the resulting magneticfield {right arrow over (H)}₁ at the reciprocal conductive coil (e.g.,the contact lens) is parallel to the vector {circumflex over (n)}, whichis orthogonal to the plane defined by the reciprocal conductive coil.The resulting magnetic field {right arrow over (H)}₁ is equal inmagnitude and direction to the sum of the magnetic field produced by thesource conductive coil 702 and the magnetic field produced by the sourceconductive coil 704. For example, if the phase difference between thefirst alternating current and the second alternating current is 90degrees, then the magnetic field produced by the source conductive coil704 may be approximately zero at time t₁ (as a result of the magnitudeof the alternating current driving the source conductive coil 704 attime t₁ being approximately zero), in which case the resulting magneticfield {right arrow over (H)}₁ is substantially equivalent to themagnetic field produced by the source conductive coil 702 at time t₁.

Continuing with the example of FIG. 8, at time t₂, the phase of thealternative currents driving the source conductive coils 702 and 704have shifted by approximately 90 degrees. As a result, the magnitude ofthe magnetic field produced by the source conductive coil 702 hasdecreased to approximately zero (as a result of the magnitude of thealternating current driving the source conductive coil 702 at time t₂being approximately zero), and the resulting magnetic field {right arrowover (H)}₂ is substantially equivalent to the magnetic field produced bythe source conductive coil 702. In other words, as the magnitude of themagnetic field produced by the source conductive coil 702 decreased toapproximately zero from time t₁ to time t₂, the magnetic field producedby the source conductive coil 704 increased from approximately zero,producing the effect that the direction of the resulting magnetic field{right arrow over (H)} rotates from the position of the resulting vector{right arrow over (H)}₁ at time t₁ to the position of the resultingvector {right arrow over (H)}₂ at time t₂.

At each of times t₃, t₄, and t₅, the phases of the alternating currentsdriving the source conductive coils 702 and 704 have shifted by afurther 90 degrees. As a result, the resulting magnetic field {rightarrow over (H)} further rotates from the position of the resultingvector {right arrow over (H)}₂ at time t₂ to the position of theresulting vector {right arrow over (H)}₃ at time t₃, to the position ofthe resulting vector {right arrow over (H)}₄ at time t₄, and to theposition of the resulting vector {right arrow over (H)}₅ at time t₅.

In the example of FIG. 8, the alternating currents used to drive thesource conductive coils 702 and 704 differ in phase by 90 degrees.Assuming that the planes defined by the source conductive coils 702 and704 are orthogonal to each other, the direction of the resultingmagnetic field vector {right arrow over (H)} can rotate linearly (e.g.,along a circular trajectory). It should be noted that in otherembodiments, the phase difference between the alternating currents usedto drive the source conductive coils 702 and 704 can be more or lessthan 90 degrees, or the angle between the planes defined by the sourceconductive coils 702 and 704 can be more or less than 90 degrees. Insuch embodiments, so long as the phase difference between thealternating currents is non-zero, and so long as the planes defined bythe source conductive coils 702 and 704 are not co-planar, the directionof the resulting magnetic field vector {right arrow over (H)} willrotate, for instance along an elliptical trajectory.

In embodiments where the direction of the resulting magnetic fieldvector {right arrow over (H)} rotates, the strength of inductivecoupling between the contact lens and the power source sinusoidallyalternates between a strong coupling and a weak coupling. Accordingly,by having the direction of the resulting magnetic field vector {rightarrow over (H)} rotate, the contact lens is able to inductively coupleto the power source cyclically, exhibiting a sinusoidal variationsimilar to a stationary magnetic field amplitude that variessinusoidally over time. Unlike a stationary magnetic field (whichdepends on the orientation of the contact lens 120 and the powersource), the strength of coupling with a rotating magnetic field isindependent of the orientation of the contact lens 120 and the powersource. In some embodiments, the contact lens includes a battery orcapacitor to smooth out variations in power caused by the rotatingmagnetic field.

FIG. 11 shows a measured voltage provided to a simulated electroniccontact lens at various contact lens orientations in the presence ofboth a stationary magnetic field and a rotating magnetic field. In theexample of FIG. 11, the dotted line represents a voltage produced by acontact lens in the presence of a stationary magnetic field as theorientation of the contact lens rotates between zero degrees and 315degrees. The coupling between the contact lens and the power sourceproducing the stationary magnetic field is weakest when the contact lensis rotated 45 degrees and 235 degrees from an initial orientation, andthe contact lens produces a voltage of 200 voltage units at theseorientations. As the contact lens rotates from these orientations, thestrength of coupling between the contact lens and the power sourceincreases, and likewise, the voltage produced by the contact lens fromthe stationary magnetic field increases. As used herein, “stationary”refers to a magnetic field that is constant in direction, and notnecessarily constant in amplitude or sign.

In the measurement illustrated by FIG. 11, the solid line represents avoltage produced by a contact lens in the presence of a rotatingmagnetic field as the orientation of the contact lens rotates betweenzero degrees and 315 degrees. As shown in FIG. 11, the voltage producedby the contact lens in the presence of the rotating magnetic fieldvaries between ˜575 voltage units and ˜750 voltage units, regardless ofthe orientation of the contact lens. Thus, in embodiments where thethreshold voltage required to power the components of the contact lensvaries between 200 voltage units and 575 voltage units, the rotatingmagnetic field of FIG. 11, unlike the stationary magnetic field, canenable the contact lens to fully operate regardless of the orientationof the contact lens.

Returning to the embodiment of FIG. 7, in some embodiments, thecontroller 700 can drive the source conductive coils 702 and 704 toproduce a rotating magnetic field at the contact lens 120 without havingto drive the source conductive coils at the same frequency but with aphase difference. For instance, the resulting magnetic field at thecontact lens 120 can be a rotating magnetic field if the controller 700varies a magnitude of each of the currents used to drive the sourceconductive coils 702 and 704. For example, the controller 700 can drivethe source conductive coil 702 with a first current at a first magnitudeand can drive the source conductive coil 704 with a second current at azero magnitude. The resulting magnetic field at the contact lens 120will be approximately equal to the magnetic field produced by the sourceconductive coil 702 (since the source conductive coil 704 doesn'tproduce a magnetic field without a driving current). The controller 700can then increase the magnitude of the second current without adjustingthe magnitude of the first current, causing the source conductive coil704 to produce a magnetic field that increases as the magnitude of thesecond current increases. This causes the direction of the resultingmagnetic field at the contact lens 120 to rotate towards the directionof the magnetic field produced by the source conductive coil 704. Thecontroller 700 can then reduce the magnitude of the first current tozero, causing the magnitude of the magnetic field produced by the sourceconductive coil 702 to reduce to zero, and in turn causing the directionof the resulting magnetic field at the contact lens 120 to furtherrotate towards the direction of the magnetic field produced by thesource conductive coil 704. Accordingly, the controller 700 can continueto adjust the magnitudes of the currents used to drive the sourceconductive coils 702 and 704, and the resulting magnetic field at thecontact lens 120 will continue to rotate. It should be noted thebenefits of a rotating magnetic field at the contact lens 120 asdescribed above may apply equally to such embodiments.

It should be noted that the controller 700 can drive the sourceconductive coils 702 and 704 without necessarily producing a rotatingmagnetic field at the contact lens 120. For instance, the controller 700can drive the source conductive coils 702 and 704 using a pre-determineddrive current pattern such that the resulting magnetic field alternatesin direction between directions that correspond to a most likelyorientation range for a contact lens (e.g., such as the orientationsillustrated in FIGS. 5A and 5C).

Alternatively, the controller 700 can drive the source conductive coils702 and 704 based on a feedback signal received from the contact lens.In some embodiments, the feedback signal includes a representation of anorientation of the contact lens 120 or the eye and head of the userwearing the contact lens. For instance, the contact lens 120 can includean orientation or position tracking component, a motion trackingcomponent, accelerometers, gyroscopes, inertial measurement units, andthe like (collectively, an “eye orientation component”). A feedbackcircuit within or associated with the contact lens 120 can transmit asignal representative of the orientation of the eye to the controller700 (for instance, via a conductive coil of the contact lens configuredto operate as a transceiver), and the controller can drive the sourceconductive coils 702 and 704 based on the representation of theorientation of the eye.

For example, in embodiments in which a signal received from the contactlens indicates that the orientation of the eye has not changed during aninterval of time in which the controller 700 drives the sourceconductive coils 702 and 704 with corresponding driving currents, thecontroller 700 can continue to drive the source conductive coils 702 and704 with the same driving currents in order to maintain the samestrength of inductive coupling with the contact lens 120. In embodimentsin which a signal received from the contact lens indicates that theorientation of the eye has shifted in a direction more parallel to thevector orthogonal to the plane defined by the source conductive coil704, the controller 700 can increase the magnitude of the current usedto drive the source conductive coil 704 to improve the strength ofinductive coupling between the contact lens 120 and the sourceconductive coils. Likewise, in embodiments in which a signal receivedfrom the contact lens indicates that the orientation of the eye hasshifted in a direction more parallel to the vector orthogonal to theplane defined by the source conductive coil 702, the controller 700 canincrease the magnitude of the current used to drive the sourceconductive coil 702 to improve the strength of inductive couplingbetween the contact lens 120 and the source conductive coils.

In some embodiments, the controller 700 can access a mapping of eyeorientations to source conductive coil drive currents in response toreceiving the eye orientation feedback signal. The drive currents mappedto a particular eye orientation can, when applied to correspondingsource conductive coils by the controller 700, cause a sufficientresulting magnetic field at the contact lens 120 to be produced for thecontact lens to produce enough power to power components of the contactlens. The controller 700 can then query the mapping with the receivedeye orientation to identify a drive current for each of one or moresource conductive coils, and can drive the corresponding sourceconductive coils with the identified drive currents.

In some embodiments, the controller 700 can drive the source conductivecoils 702 and 704 based on a power feedback signal received from thecontact lens 120. The power feedback signal can be transmitted by afeedback circuit within or associated with the contact lens 120 based oninformation provided by a power generation circuit of the contact lens.The power feedback signal can be representative of the amount of powerbeing produced by the contact lens, the amount of current within areciprocal coil of the contact lens, a strength of inductive couplingbetween the contact lens and the source conductive coils, an indicationthat more power is required to power components of the contact lens, andthe like. The controller 700 can maintain or alter the amount of currentused to drive each source conductive coil 702 and 704 (and thus maintainor adjust the magnetic fields produced by the source conductive coils702 and 704) based on this representation of the power produced by thecontact lens 120.

For instance, in embodiments in which the power feedback signal receivedfrom the contact lens 120 indicates that the contact lens, in thepresence of the magnetic fields produced by the source conductive coils702 and 704 in response to driving currents from the controller 700, isproducing a sufficient amount of power to power the components of thecontact lens, the controller 700 can continue to drive the sourceconductive coils 702 and 704 without adjusting the driving currents. Inthese instances, since the resulting magnetic field at the contact lens120 can be harnessed to address the power needs of the contact lens,there is no need to change the magnetic fields produced by the sourceconductive coils 702 and 704 (and indeed, a change to a magnetic fieldproduced by a source conductive coil might negatively affect the abilityof the contact lens 120 to produce enough power for the components ofthe contact lens).

In embodiments in which the power feedback signal received from thecontact lens 120 indicates that the contact lens is producing less thana threshold amount of power necessary to power components of the contactlens, the controller 700 can adjust the driving current supplied to oneor both of the source conductive coils 702 and 704. For instance, thecontroller 700 can increase the current supplied to one or both of thesource conductive coils 702 and 704. In some embodiments, the powerfeedback signal indicates that the contact lens 120 is producing lessthan a maximum power, and the controller 700 can adjust the drivingcurrent supplied to the source conductive coils until the power feedbacksignal indicates that the contact lens is producing the maximum power.In other embodiments, the controller 700 can increase the currentsupplied to a first of the source conductive coils 702 and 704 whiledecreasing the current supplied to a second of the source conductivecoils (for instance, in embodiments where the available amount ofcurrent the controller can use to drive the source conductive coils islimited).

In some embodiments, in response to receiving the power feedback signalindicating that the contact lens is not producing enough power, thecontroller 700 can identify a source conductive coil being driven by thesmallest amount of current and can increase the current used to drivethe identified source conductive coil. In other embodiments, thecontroller 700 can iteratively adjust the currents used to drive a firstset of source conductive coils, can receive a subsequent power feedbacksignal, and in response to the subsequent power feedback signalindicating that the contact lens is still not producing a sufficientamount of power, can adjust the currents used to drive a second set ofsource conductive coils. For example, the controller 700 can 1) increasethe current used to drive a first source conductive coil in response toreceiving a first power feedback signal indicating that the contact lens120 is not producing enough power, can 2) decrease the current used todrive the first source conductive coil and/or can increase the currentused to drive a second source conductive coil in response to receiving asecond subsequent power feedback signal indicating that the contact lensis not producing enough power, can 3) decrease the current used to drivethe second source conductive coil and/or can increase the current usedto drive a third source conductive coil in response to receiving a thirdsubsequent power feedback signal indicating that the contact lens is notproducing enough power, and 4) can iteratively repeat this process byadjusting the drive currents for one or more source conductive coilsuntil a power feedback signal is received that indicates the contactlens is producing a sufficient amount of power.

The contact lens 120 can provide feedback, such as power feedback or eyeorientation feedback, to the controller 700 periodically (for instance,every second or less, every 5 seconds, every 10 seconds, every minute,etc.). In other embodiments, the contact lens 120 provides feedback inresponse to a request from the controller 700, in response to theoccurrence of an event (such as an above-threshold change inorientation, an amount of power produced by the contact lens fallingbelow a threshold, and the like), or in response to any other suitablecriteria. As noted above, the contact lens 120 can provide feedbackusing a dedicated feedback circuit, or can use a local transmitter ortransceiver, can encode the feedback within magnetic fields produced bya reciprocal coil of the contact lens (e.g., by providing drive currentsto the reciprocal coil), or can provide the feedback using any othersuitable means available to the contact lens.

It should be noted that the functionalities associated with driving ofone or two source conductive coils to produce a resulting magnetic fieldat a contact lens 120 as described herein also apply to the driving ofthree or more coils. For instance, FIG. 9A shows a side view of a systemwith three conductive coils for providing power to an electronic contactlens and FIG. 9B shows a front view of a system with three conductivecoils for providing power to an electronic contact lens.

In the embodiments of FIGS. 9A and 9B, a controller 900 drives threesource conductive coils 902, 904, and 906. The source conductive coils902, 904, and 906 as illustrated in FIGS. 9A and 9B are worn around auser's neck, on a user's chest, and around a user's shoulder,respectively. In this arrangement of source conductive coils, the threevectors orthogonal to each of the planes defined by the sourceconductive coils are orthogonal to each other. Such an arrangement ofsource conductive coils enables the source conductive coils to be drivenin such a way to produce a resulting magnetic field at the contact lens120 in any desired direction.

In some embodiments, the controller 900 can drive the source conductivecoils 902, 904, and 906 with currents at a same frequency but with aphase difference between the currents. In such embodiments, thedirection of the resulting magnetic field at the contact lens 120 willrotate in some repeating pattern in three dimensions, enabling thecontact lens 120 to strongly inductively couple to the source conductivecoils 902, 904, and 906 for at least some portion of the currentfrequency cycle independent at any orientation of the contact lens. Asnoted above, the source conductive coils 902, 904, and 906 can insteadbe driven by varying the magnitudes of the currents provided to thesource conductive coils in order to produce a resulting magnetic fieldthat rotates in three dimensions. Finally, as described above, thesource conductive coils 902, 904, and 906 can also be driven by thecontroller 900 based on a pre-determined drive current pattern or basedon power feedback or eye orientation information received from thecontact lens 120 in order to produce a resulting magnetic field at thecontact lens sufficient for the contact lens to produce enough power topower the components of the contact lens.

Although many of the embodiments described above are described in termsof wearable source conductive coils, in practice, the source conductivecoils can be located within an environment of a wearer of the contactlens 120 and still perform the functionalities as described here. Forinstance, FIGS. 10A and 10B show rooms with multiple source conductivecoils for providing power to an electronic contact lens. In FIG. 10A, asource conductive coil is located on each wall of the room of FIG. 10A.For instance, the source conductive coil 1002 is located on the ceilingof the room, source conductive coils 1004, 1006, and 1008 are located onthe side and front walls of the room, and source conductive coil 1010 islocated on the floor. In FIG. 10B, a source conductive coil is locatedon surfaces of objects within the room. For instance, source conductivecoil 1012 is located on a top surface of a side table, source conductivecoil 1014 is located on an upper surface of a coffee table, and sourceconductive coil 1016 is located on a lower surface of the coffee table.The source conductive coils can also be located on various surfaceswithin an automobile. FIG. 10C shows an interior of a car with multiplesource conductive coils for providing power to an electronic contactlens. For instance, source conductive coil 1020 is located around asteering wheel, source conductive coil 1022 is located on a frontdashboard of the car, source conductive coil 1024 is located on a doorof the car, and source conductive coil 1026 is located on a centerconsole of the car.

In the embodiments of FIGS. 10A, 10B, and 10C, one or more of the sourceconductive coils within the environment of a wearer of a contact lenscan produce magnetic fields for power conversion by the contact lens. Asdescribed above, a resulting rotating magnetic field can be produced bydriving two or more of the coils with currents at a same frequency butwith a different phase, or by adjusting the amplitudes of the currentsover time. Likewise, the contact lens can provide feedback to the sourceconductive coils within these environments, for instance power feedbackand eye orientation feedback. In response to and based on this feedback,the source conductive coils can be driven with different currents, orone or more different source conductive coils can be driven to producemagnetic fields. By locating the source conductive coils within anenvironment of a wearer of a contact lens, the source conductive coilscan access an external power source, and may not be limited to aportable/wearable power source as are many of the embodiments of thesource conductive coils described above.

The augmented reality system 100 may include multiple elements. Anelement may comprise any physical or logical structure arranged toperform certain operations. Each element may be implemented as hardware,software, or any combination thereof, as desired for a given set ofdesign parameters or performance constraints. Examples of hardwareelements may include devices, components, processors, microprocessors,circuits, circuit elements (e.g., transistors, resistors, capacitors,inductors, and so forth), integrated circuits, application specificintegrated circuits (ASIC), programmable logic devices (PLD), digitalsignal processors (DSP), field programmable gate array (FPGA), memoryunits, logic gates, registers, semiconductor device, chips, microchips,chip sets, and so forth. Examples of software may include any softwarecomponents, programs, applications, computer programs, applicationprograms, system programs, machine programs, operating system software,middleware, firmware, software modules, routines, subroutines,functions, methods, interfaces, software interfaces, application programinterfaces (API), instruction sets, computing code, computer code, codesegments, computer code segments, words, values, symbols, or anycombination thereof.

What is claimed is:
 1. A system, comprising: a plurality of wearableconductive coils each configured to generate a corresponding magneticfield that collectively comprise a resulting magnetic field; anelectronic contact lens, comprising: a power circuit configured toproduce power in response to the resulting magnetic field; and afeedback circuit configured to transmit a power signal representative ofthe produced power; and a controller electrically coupled to theplurality of conductive coils and configured to receive the power signaland to drive the plurality of conductive coils based on the receivedpower signal.
 2. The system of claim 1, wherein the power signalindicates an amount of power produced by the power circuit.
 3. Thesystem of claim 2, wherein the controller is configured to adjust thecorresponding magnetic fields produced by a set of the conductive coilsin response to the amount of power produced by the power circuit beinglower than a threshold amount of power.
 4. The system of claim 2,wherein the controller is further configured to adjust the correspondingmagnetic fields produced by a set of the conductive coils in response tothe amount of power produced by the power circuit being lower than amaximum amount of power.
 5. The system of claim 2, wherein thecontroller is configured to maintain the magnetic fields produced by aset of the conductive coils in response to the amount of power producedby the power circuit being greater than a threshold amount of power. 6.The system of claim 1, wherein driving the plurality of conductive coilsbased on the received power signal comprises adjusting a magnitude ofcurrent within one or more of the conductive coils to adjust themagnetic field produced by the one or more of the conductive coils. 7.The system of claim 1, wherein driving the plurality of conductive coilsbased on the received power signal comprises increasing a current withina first of the conductive coils and decreasing a current within a secondof the conductive coils.
 8. The system of claim 1, wherein theelectronic contact lens includes an embedded conductive coil, andwherein the power circuit and the feedback circuit are each coupled tothe embedded conductive coil.
 9. The system of claim 1, wherein theresulting magnetic field is equal to a sum of the corresponding magneticfields.
 10. The system of claim 1, wherein the feedback circuit isfurther configured to transmit an orientation signal representative ofan orientation of the electronic contact lens, and wherein thecontroller is further configured to receive the orientation signal andto drive the plurality of conductive coils based additionally on thereceived orientation signal.
 11. A method for providing power to anelectronic contact lens, comprising: providing, by a controller, a drivesignal to each of a plurality of wearable conductive coils to producecorresponding magnetic fields that collectively comprise a resultingmagnetic field; receiving, by the controller, a power signalrepresentative of power generated by the electronic contact lens inresponse to the resulting magnetic field; and adjusting, by thecontroller, the corresponding magnetic fields produced by the pluralityof conductive coils by adjusting the drive signals provided to each ofthe plurality of conductive coils to adjust.
 12. The method of claim 11,wherein the power signal indicates an amount of power produced by theelectronic contact lens.
 13. The method of claim 12, wherein thecontroller is configured to adjust the corresponding magnetic fieldsproduced by the conductive coils in response to the amount of powerproduced by the electronic contact lens being lower than a thresholdamount of power.
 14. The method of claim 12, wherein the controller isconfigured to maintain the corresponding magnetic fields produced by aset of the conductive coils in response to the amount of power producedby the electronic contact lens being greater than a threshold amount ofpower.
 15. The method of claim 11, wherein adjusting the correspondingmagnetic fields comprises adjusting a magnitude of a current provided toone or more of the conductive coils to adjust the magnetic fieldproduced by the one or more of the conductive coils.
 16. The method ofclaim 11, wherein adjusting the magnetic fields comprises increasing acurrent within a first of the conductive coils and decreasing a currentwithin a second of the conductive coils.
 17. The method of claim 11,wherein the electronic contact lens includes an embedded conductivecoil, and wherein the embedded conductive coil produces power inresponse to the resulting magnetic field.
 18. The method of claim 11,wherein the resulting magnetic field comprises a sum of the magneticfields corresponding to the plurality of conductive coils.
 19. Themethod of claim 11, wherein the electronic contact lens is configured totransmit an orientation signal representative of an orientation of theelectronic contact lens, and wherein the controller is furtherconfigured to receive the orientation signal and to drive the pluralityof conductive coils based additionally on the received orientationsignal.
 20. A system, comprising: a plurality of wearable conductivecoils each configured to generate a corresponding magnetic field, thecorresponding magnetic fields collectively comprising a resultingmagnetic field; an electronic contact lens, comprising: a power circuitconfigured to produce power in response to the resulting magnetic field;and an eye tracking component configured to determine a position of atracked eye; and a controller electrically coupled to the plurality ofconductive coils and configured to drive the plurality of conductivecoils based on the determined position of the tracked eye.